In our session, a dragon used Crush to pin a paladin. During his turn, could the paladin use Lay on Hands to heal himself and attack the dragon with a melee weapon?

Consensus was divided between "the only thing he could do is try a combat maneuver check to free himself" and "he can do anything that is not expressly forbidden in the pinned and grappled condition" (so he could use Lay On Hands (because it only requires a single hand) and attack with a one-handed weapon).

So unless something says otherwise, you are limited to the options on the condition, which are listed right after that:

A pinned creature can always attempt to free itself;

A pinned creature can take verbal and mental actions, but cannot cast any spells that require a somatic or material component.

So you could take Swift Actions if those are verbal or mental or attempt to free yourself. But since it does not say "You can take swift actions", you are limited to only those swift actios that do specify that they are purely mental or verbal in nature, or have a description that suggests that the character only has to speak or think for it to work, such as:

Every other swift action should be impossible, such as an alchemist trying to apply poison to a weapon, or the same warpriest enhancing his weapon with magical power.

Lay on Hands specifically says that you need a free hand, which by the definition of the Pinned condition, you probably won't have (but you would while grappled).

Despite the name of this ability, a paladin only needs one free hand to use this ability

Regardless, the character still should be allowed to use a spell-like ability (no somatic or material components) if they pass their concentration check.

This seems to be the concensus of the community aswell, as can be observed here, here, and finally here. On the last, Sean K. Reynolds state that a touch attack is not a mental or verbal action and the thread's FAQ request was answered "Staff response: no reply required.".

Nope, because one of the things that happened when you are pinned is that you are VERY limited as to what actions you can take. Most importantly, you can't attack if you're pinned—in order to attack, you first need to escape the pinned condition. So... no. If you're pinned, you can't make a full attack.

For all purposes, the rules as intended is that you can only take the actions listed on the Pinned condition.

If the intent of Pinned was to allow you to take the same actions allowed by grapple, the devs wouldn`t even mention that you can take mental and verbal actions, as those are already allowed while grappled. They would simply state that you can only cast spells without somatic components and take a heavier penalty to AC.

This would save text (like half of it) and still be clear about the intent of the condition.

A pinned creature cannot move and is denied its Dexterity bonus. A pinned character also takes an additional –4 penalty to his Armor Class...A pinned creature can take verbal and mental actions, but cannot cast any spells that require a somatic or material component...Pinned is a more severe version of grappled, and their effects do not stack.

So pinned is more severe than grappled.

The grappled condition states that you can make attacks at a -2 bonus and can take no actions that require two hands to perform:

A grappled creature takes a –2 penalty on all attack rolls and combat maneuver checks, except those made to grapple or escape a grapple. In addition, grappled creatures can take no action that requires two hands to perform.

The pinned condition says that its effects do not stack with grappled, and that it is a more severe form of grapple. From this, we can infer that the more severe parts of pinned are the parts it specifically defines:

Denied it's DEX bonus (pinned) vs. -4 penalty to Dexterity (grappled)

-4 penalty to AC (pinned) vs. no additional AC penalty (grappled)

Other than these two changes, the rules for pinned are the same as for grappled, which means actions taken with one hand are fine. This means the -2 to attack is still in effect, which means attacking, at least per the written rules, is not forbidden. It also means he can Lay on Hands.

However, extenuating circumstances may apply as determined the the GM. Consider the following: a paladin who is tied up with rope has the pinned condition. The paladin can probably still lay on hands, unless something is specifically restraining his hands in a way that he cannot touch himself with them. He may be able to attack but again, if he's restrained in such a way as to make that not possible (for example, hogtied and hanging upside down from a tree) then there's not much he can do.

Given the example scenario of a dragon's Crush attack, I don't see why he couldn't attempt to stab it with his sword and lay hands on himself, per the rules of the pinned condition.

\$\begingroup\$i don`t see it being more severe if they are nearly identical if we follow what this answer suggests. Why would it say you can take mental and verbal actions if those were already allowed by grapple? If that was the case, it wouldn't mention that and would only restrict your spell casting to those without somatic components. Which would save text and still be clear about the intent of the rule.\$\endgroup\$
– ShadowKrasDec 2 '16 at 15:36

\$\begingroup\$@ShadowKras It is still more severe. -4 is more severe than -2, is it not? It doesn't state to which degree it is more severe, and if it's supposed to be "more severe" then should it not define what that means? Hence, my answer. Pinned is a condition that can vary from being sat on top of (you can still punch your opponent) to being completely bound in ropes and chains (you can barely move). Note that, logically, stating you can take mental and verbal actions does not preclude other actions. If it should, it would say, "you can take mental and verbal actions, but nothing else."\$\endgroup\$
– LegendaryDudeDec 2 '16 at 15:52

\$\begingroup\$Then what would be the difference between those two pinned conditions on the rules? Why one allows you to attack and the other doesn't? There is no "pinnned but cant act" condition as far as i know.\$\endgroup\$
– ShadowKrasDec 2 '16 at 15:55

\$\begingroup\$@ShadowKras That's what the GM is for, and I've noted such in my answer.\$\endgroup\$
– LegendaryDudeDec 2 '16 at 15:55

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\$\begingroup\$A paladin that is tied up with rope is Helpless, which is a more severe condition than Pinned.\$\endgroup\$
– RMorriseyJul 2 '17 at 6:24